Posts Tagged ‘Yamaha’

Marion Prosynth, Sequential Circuits Prophet 2000 and a Yamaha TX7

We hope you all had a nice holiday, we all had a much needed break here at Analog Sweden. Unfortunately the weather is quite cold here at the moment, but hey we are in Sweden so what should we expect in the winter months. So we have a mixed bag to report on today, some analog, some digital and some digital with analog filters. Quite a mixed bunch.

First up is a stack of Marion Pro Synths, these were designed by Tom Oberheim and the core technology is based very much around his matrix 1000 synths. This are a little better though since you get a nice large LCD for editing. These units are NOS and had been sitting so long that i had to replace all the batteries, originally they were hardwired, but i figured to place holders in there so that the next time the battery needs replacing its a simple job that doesn’t involve any soldering.

Next up was a Yamaha TX7, this needed some general maintenance, i suppose you all know this is basically a DX7 in a small form factor, the less said about this the better, unless we plan to change our name to Digital Sweden…not any time soon thankfully :-)

The current job on the workbench is a Sequential Circuits Prophet 2000. This is an old school sampler, but has nice curtis based analog filters. Three of the eight voices were dead, I’ve since repaired them and have now encountered another problem (this is often the case with vintage gear, fix one thing, find another problem) Thenewly discovered fault is with the sampling input, i can sample but it only samples silence. I’ve traced the input signal and so far I’ve confirmed it up to the input filters. that cuts out quite a large section of the circuit, but there’s still plenty more to debug and so that’s my current quest.

Well I guess its time to get back to it, keep your eyes open over the coming weeks since there will be some major changes around here, including some updates to the site and a new web shop where you’ll be able to browse the goodness we have for sale.


01 2010

Yamaha CS-60 Calibration

Remember ABBA? how could you forget? Well this machine remembers them very well, since we have it on authority that this actual machine used to belong to Benny Andersson of ABBA. It didn’t have any serious issues apart from being completely out of tune. So it was my task to calibrate it back to factory settings. Quite a task since this is one of those machines that wasn’t designed from a service point of view. Still after considerable work it sings again like it should. Now wheres my platform shoes ;-D

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11 2009

Yamaha CS01, Roland JD800 and Oberheim 4-Voice

A few more machines on the workbench. First up was a Roland JD-800 with a broken pitch-bend unit. Quite a simple fix and easy to source the part. A clients Yamaha CS-01 with a missing key, hopefully the spare part will arrive soon and I’ll get that up and running again. And then an Oberheim 4-Voice which had been partially repaired by someone else. There were still some problems with one of the SEMS which I’ve managed to rectify. In fact everything about the 4-voice Sems is now taken care of, but there’s a problem with the programmer unit which I’ll be taking a deeper look at soon. Also it seems like the Oberheim is possessed, see the attached picture.


09 2009

Yamaha CS70m Kenton Midi retrofit group buy

Finally a way to realize the potential of the mighty CS70m!

You now have the opportunity to get a Yamaha CS70m Midi retrofit by Kenton Electronics UK. It will be a redesign of the Kenton kit that was discontinued due to parts availability quite some years ago.

Scroll down to the end of the document to read the specifications.

This is a group buy, which means that we need at least 10 prepaid orders to start the production. Production and distribution will be approx 8 weeks.


349 UK pounds + VAT which needs to be paid in advance to Analog Sweden. If we don’t reach 10 prepaid orders by the 1st of  November 2009, your money will be promptly returned.  Shipping cost not included.

Ordering & Questions

Use the contact form here

November 1, 2009

The kits are not intended for installation by the end user. They should always be fitted by an experienced synth engineer. The kits are built and tested before dispatch. DIY-kit NOT available. Analog Sweden can do the installation.

We at Analog Sweden have had a few enquiries about CS70m retrofits, so we got in touch with Kenton to investigate the possibilites for a new production run. Kenton wanted to have a group order to start the production, and here we go.
Analog Sweden is a studio and repair workshop in Helsingborg, Sweden. You can see what we do at

If in doubt, you can verify our claims if you get in touch with Kenton.


This retrofit kit for the Yamaha CS-70M adds the following MIDI control:

For incoming MIDI:

Any MIDI channel can be selected

Notes on MIDI note numbers normally 36 – 96 but transpose possible

Program change numbers 1 – 32
where 1 – 16 = upper + manual, 17 – 32 = lower + manual

Pitchbend -

Mod Wheel -

Filter cutoff frequency (of low pass filter)




This kit is to receive MIDI only, no MIDI can be sent, however a Thru
socket is included.

MIDI In, & Thru sockets
Push button (for programming the MIDI setup)
Setups are stored in non-volatile memory (Eeprom)

The kit comprises the following items
Circuit board -
Small pack – contains DIN sockets and mounting hardware
Large pack – contains cable assemblies
User instructions – How to change from default settings and general
Fitting instructions – step by step fitting guide plus diagrams of where
to connect what.

All kits are fully checked and tested before despatch.

Note: The retrofit kits are not intended for installation by the end
user. They should always be fitted by an experienced synth engineer.

Errors & Omissions excepted



08 2009

The CS70M Saga Continues

So the new caps arrived for the CS70. After fitting them and double checking their polarity it was time to reassemble the monster and power it up. It seemed to go well, the fault was gone? We were about to celebrate when 10 minutes later the reset problem returned.  I believe now that the problem lies with the CPU section since its fine in manual mode. I took a look in there and to be honest it’s one of those problems not mentioned in the service manual/troubleshooting notes. I hate to admit defeat since I’ve invested many hours in trying to get this thing up and running. But alas, it would seem for now the CS70 has beaten me. The CPU section has many (and I really mean many) IC’s any of which could be the cause of this behaviour. Its practically impossible to know what’s wrong. If anyone has any suggestions I’m all ears. Until then it’s only useful as a performance synth.

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03 2009

The British Empire was Built on Cups of Caps

A slightly mangled version of a quote from a very funny British movie. For those of you who don’t already know I’m actually English and cups of tea are part of my daily routine. Anyway back to the business at hand. All the caps have been removed from the CS70M power supply and I’m waiting for an order of new ones to arrive. Whether that will fix the problem remains to be seen, but as previously mentioned it was a job that needed doing regardless. In the meantime I took the second Prophet VS apart and removed the broken data slider and volume knob. An order for those parts is in progress also, so as soon as that arrives we’ll have two VS’s up and running. I also managed to take an inventory of all the missing knobs/parts of the remaining equipment in the studio, it’s quite some list, but then there’s quite some gear in there after all.


03 2009

Bust a cap in yo a**!

So I took out the control pcb’s and gave everything a good clean up. Lubricated the faders, wiped away years of dust, re-flowed a few solder joints and gave the cabinet and switch-caps a good clean. However I was unable to locate the cause of the reset problem, until I looked at the power supply. Looks like the caps are in need of replacing, one has leaked all over the pcb, so it’s time to make an order for new ones. This may not be the cause of the reset problem but even if not it’s a job that needs doing right away.

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03 2009

Phono wins! (almost)

Suck me!

Well I’m happy to report that I managed to resurrect the dead voice board in the CS70M. It was quite a task but with a bit of perseverance I finally found the fault. The oscillator IC was blown, replacing it with an identical chip from the old cs60 voice board made it sing again. Hooray! However another intermittent fault has reared its ugly head. The synth seems to “reset” sometimes when cold. Not sure what’s causing it, hopefully I’ll be able to track that down today and get the repairs done before the weekend.

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03 2009